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Aims/hypothesisType 1 diabetes is an autoimmune disorder characterised by loss of insulin-producing beta cells of the pancreas. Progress in understanding the cellular and molecular mechanisms underlying the human disease has been hampered by a dearth of appropriate human experimental models. We previously reported the characterisation of islet-infiltrating CD4+ T cells from a deceased organ donor who had type 1 diabetes.MethodsInduced pluripotent stem cell (iPSC) lines derived from the above donor were differentiated into CD14+ macrophages and tested for their capacity to present antigen to T cell receptors (TCRs) derived from islet-infiltrating CD4+ T cells from the same donor.ResultsThe iPSC macrophages displayed typical macrophage morphology, surface markers (CD14, CD86, CD16 and CD11b) and were phagocytic. In response to IFNγ treatment, iPSC macrophages upregulated expression of HLA class II, a characteristic that correlated with their capacity to present epitopes derived from proinsulin C-peptide to a T cell line expressing TCRs derived from islet-infiltrating CD4+ T cells of the original donor. T cell activation was specifically blocked by anti-HLA-DQ antibodies but not by antibodies directed against HLA-DR.Conclusions/interpretationThis study provides a proof of principle for the use of iPSC-derived immune cells for modelling key cellular interactions in human type 1 diabetes.Electronic supplementary materialThe online version of this article (10.1007/s00125-019-04988-6) contains peer-reviewed but unedited supplementary material, which is available to authorised users.

Vitamin D has an important role to play in skeletal and extraskeletal health. Inspite of being a sun rich country, India has widespread vitamin D deficiency. Vitamin D deficiency can lead to serious consequences like hypocalcemic seizures and increased risk of respiratory tract infections in neonates and infants. International expert groups advocate universal supplementation for non-formula fed infants, pregnant and lactating women and those at risk of deficiency. A body of literature on vitamin D status in India is being generated, which may guide clinical practice in our country. Treatment of deficiency must be undertaken with minimally effective doses to avoid the risk of toxicity. Sensible sunshine exposure should be encouraged to facilitate vitamin D production from natural sources.

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Background: Somatotropinomas are rare in childhood and frequently associated with genetic mutations. AIP mutations are found in 20–25% cases and cause aggressive somatotropinomas, often resistant to somatostatin analogues. Aims: To assess responses to multimodal therapy including pegvisomant in 2 children with sporadic somatotropinomas due to AIP mutations. Case Description: We report 2 children, a boy aged 13 and a girl aged 10, with rapid growth, visual impairment, and growth hormone hypersecretion. Magnetic resonance imaging confirmed a pituitary macroadenoma with parasellar extension in both. Despite multiple surgical attempts to debulk tumour mass, residual tumour persisted. Genetic analysis showed two different AIP mutations (patient 1: c.562delC [p.Arg188Glyfs*8]; patient 2: c.140_ 163del24 [p.Gly47_Arg54del8]). They were initially treated with a long-acting somatostatin analogue (octreotide LAR 30 mg/month) and cabergoline as a dopamine agonist, with the later addition of pegvisomant titrated up to 20 mg/day and with radiotherapy for long-term control. Somatostatin analogue was ceased due to patient intolerance and lack of control. Patient 1 had normalization of insulin-like growth factor-1 (IGF-1) after 5 months of combined therapy with pegvisomant and cabergoline. For patient 2, normalization of IGF-1 was achieved after 2 months of cabergoline and pegvisomant. Conclusion: AIP-associated tumours can be resistant to management with somatostatin analogues. Pegvisomant can safely be used, to normalize IGF-1 levels and help control disease.

Induced pluripotent stem cell (iPSC) technology is increasingly being used to create in vitro models of monogenic human disorders. This is possible because, by and large, the phenotypic consequences of such genetic variants are often confined to a specific and known cell type, and the genetic variants themselves can be clearly identified and controlled for using a standardized genetic background. In contrast, complex conditions such as autoimmune Type 1 diabetes (T1D) have a polygenic inheritance and are subject to diverse environmental influences. Moreover, the potential cell types thought to contribute to disease progression are many and varied. Furthermore, as HLA matching is critical for cell-cell interactions in disease pathogenesis, any model that seeks to test the involvement of particular cell types must take this restriction into account. As such, creation of an in vitro model of T1D will require a system that is cognizant of genetic background and enables the interaction of cells representing multiple lineages to be examined in the context of the relevant environmental disease triggers. In addition, as many of the lineages critical to the development of T1D cannot be easily generated from iPSCs, such models will likely require combinations of cell types derived from in vitro and in vivo sources. In this review we imagine what an ideal in vitro model of T1D might look like and discuss how the required elements could be feasibly assembled using existing technologies. We also examine recent advances towards this goal and discuss potential uses of this technology in contributing to our understanding of the mechanisms underlying this autoimmune condition.

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